Papers by Keyword: Attenuation

Abstract: The uncertainty of ground motion attenuation and its correction in PSHA is deal with in this paper. Mean values and standard deviations of random errors of three attenuation relationships of NGA-west1 are analyzed statistically from the data base released by the project. The dependences of the mean and deviation on magnitude, distance and peak ground acceleration are checked by the data base. The fact of mean values varying with acceleration is revealed obviously. Ground motion parameter Y is adopted into the probability density function of random error in a form of subsection. Finally, a suggestion to improve the correction is presented as subsection correction in the paper. The result of a case study by suggested procedure shows that the corrected acceleration is slightly higher than that of the traditional correction at the start of hazard curve, and is significantly lower than that of the traditional correction at the end of the curve, if the mean of random error decreases with acceleration.

Abstract: High density of PM2.5 that has an insignificant contribution to the increasing dusty weather threats the physicaland mental health of approximate six hundred millions Chinese recently. In this paper, we investigate thediffusion and attenuation of PM2.5 and give a prediction of its density in Xi’an city, which is based on nonstationarytwo-dimensional multi-box model, while considering the effect of seasons and wind direction. Asimulation is conducted with data from thirteen random selected stations. Furthermore, by comparing the realmeasured value and numeric value, we evaluate the validity of our proposed model as well as giving the relativeerror.Keywords: Two-Dimensional Multi-Box model, PM2.5, Diffusion, Attenuation.

Abstract: In recent years, acoustic emission (AE) testing technology is the one of the most important non-destructive testing (NDT) methods. The characteristics can be described by AE signals, including the location, nature and severity. In order to obtain the basic data for monitoring the wind turbine blade composite structure, the experiment adopted Φ0.5 mm lead pencil as artificial acoustic emission source and measured AE parameters, attenuation and source location of resin matrix for wind turbine blade. This paper introduced linear location and two-dimensional positioning technology of time arrival location method about the burst AE signal. The result shows that the location of AE source basically reflects the location of stimulation AE source, the location of AE source for resin matrix can agree well with the simulated location of AE source, the more close to the middle area, the more accurate location.

Abstract: In this article, circumferential SH wave propagation in functionally graded material (FGM) hollow cylinders is investigated. Based on the Kelvin-Voigt viscoelastic theory, the controlling differential equations in terms of displacements are deduced. By the Legendre polynomial method, the asymptotic solutions are obtained. Through the numerical results, the influences of gradient profile and the influences of the radius to thickness ratio on dispersion and attenuation are illustrated. The work is crucial for guided ultrasonic nondestructive evaluation for graded hollow cylinders.

Abstract: seismic wavess energy and frequency will attenuate with its dissemination is one of the important seismic waves dynamic characteristics, and the most influential factors including the frequency, oil and gas saturation and porosity, so we can forecast the oil and gas according to the attenuation characteristics of the wavlet. The article extracted and analysised the attenuation properties of two different time seismic, and it could be seen that the remaining oil should be distributed in the southwest. So the result had a certain guiding significance to the exploration and development of the work area.

Abstract: When measuring residual strain distributions of thick structural components such as thick butt-welds using neutron diffraction, it is required to make a gauge volume larger as well as to shorten neutron path length in a material to obtain sufficient diffraction intensity. In this study, neutron attenuation effect on the strain measurement with a large gauge volume was discussed on the normal strain measurement of a thick butt-weld. Influences of neutron attenuation like an apparent strain change were observed, and it was more noticeable when the gauge volume becomes larger. Therefore, the neutron attenuation effect should be considered in the strain measurement with a large gauge volume, and the neutron absorption corrections certainly play an important role for improvement of reliabilities of strain measurement using neutron diffraction with a large gauge volume.

Abstract: Marine development activities have a great impact on the Marine environment. Laser transmission has been widely used in marine communications and imaging technology. Due to the different proportion of the chemical composition of seawater in each Ocean field, the laser transmission characteristic in seawater is also different. The transmittance has been measured and calculated in a constant transmission distance in this experiment, by four different wavelength lasers and different concentrations of the various chemical components of the seawater. Then the data were analyzed by transmission curve fitting. The conclusion of this experiment is: for relatively pure seawater, the transmission characteristics of blue - green laser is better than the purple or red laser, and green laser transmission characteristics is better than blue laser; for larger impurities seawater such as Tianjin seawater, the transmission characteristics of red laser is better than the other three wavelength laser.

Abstract: In the galvanic coupling intra-body communication, transmitting and receiving of signals require coupling between electrodes and human tissue. Electrode size has a direct effect upon signal attenuation so as to influence signal transmission. To analyze the exact effect of electrode size on signal attenuation, the volume conductor model of human forearm is built with COMSOL Multiphysics 4.2a.It can be found from the simulation experiment that, signal attenuation declines with the increase of electrode size, which lays the foundation for subsequent experiments.

Abstract: Using artificial light source to supplement light for submerged plants in water where the illumination is insufficient can promote the growth and improve the purification ability of submerged plants. The attenuation rule of underwater irradiation is the key to design and place the lamps. High-precision underwater spectrograph was adopted to study the underwater light spectrum and attenuation rule of underwater irradiation. The results showed that the attenuation rate of total irradiation (E) with depth (h) and turbidity (t) in algae water is the most remarkable; the relationships of E with h and t in different water were E₁(t,h)=E₀e^-K(t)h=E₀e^{-(0.1345t+0.1206)h}(muddy water), E₂(t,h)=E₀e^-K(t)h=E₀e^{-(0.203t+0.4684)h}(algae water) and E₃(t,h)=E₀e^-K(t)h=E₀e^{-(0.1708t+0.2279)h}(mixed water). By these relationships, the position of artificial light could be calculated.

Abstract: Aiming at the absorption effect of fog suspended in the atmosphere on light, the paper established the removing-fog compensation adaptive model which can improve the atmospheric visibility and restore the normal work of outdoor system. The experimental results show that the removing fog image processed by the method of removing-fog compensation optimization can accord with the requirement of human visual, and it can be used in real-time video monitoring as the fast computing speed. The method not only can be used in foggy video which the fog distributed uniformly, and can assess the visual quality for the images processed.